A federal judge has restored protection under the U.S. Endangered Species Act for gray wolves in the northern Rocky Mountains, derailing plans by three states to hold public wolf hunts this fall.

U.S. District Judge Donald Molloy in Missoula, Montana, granted a preliminary injunction late Friday restoring federal protection for wolves in Montana, Wyoming, and Idaho.

Molloy will eventually decide whether the injunction should be permanent.

Early settlers had eradicated wolves from the area, but in the mid-1990s the federal government reintroduced 66 animals as part of a controversial program.

The northern Rockies region now has an estimated 2,000 gray wolves, and in February the population was dubbed a conservation success story and removed from the endangered species list.

The decision meant that state governments would be free to manage their wolf numbers, including via laws that opened wolves to hunting.

Environmentalists sued to overturn the decision, arguing that wolf numbers would plummet if hunting were allowed.

"There were fall hunts scheduled that would call for perhaps as many as 500 wolves to be killed," said Earthjustice attorney Doug Honnold, who had argued the case before Molloy on behalf of 12 environmental groups.

"We're delighted those wolves will be saved."

Genetic Exchange

In his ruling, Molloy said the federal government had not met its standard for wolf recovery, including ensuring healthy genetics by showing that wolves in the three states are interbreeding.

"Genetic exchange has not taken place," Molloy wrote in the 40-page decision.

Molloy added that a combination of hunting and state laws allowing wolves to be killed if they attack livestock would likely "eliminate any chance for genetic exchange to occur."

Ed Bangs, the U.S. Fish and Wildlife Service biologist who led the wolf restoration program, defended the decision to delist the northern Rockies wolves as "a very biologically sound package."

"The kind of hunting proposed by the states wouldn't threaten the wolf population," Bangs said.

"We felt the science was rock solid and that the delisting was warranted."

Bangs said government attorneys were reviewing Molloy's court order and would decide next week whether to file with the Ninth U.S. Circuit Court of Appeals.

Federal and state officials had argued killing some wolves would not endanger the overall population—as long as numbers did not dip below 300 individuals.

With increasing conflicts between wolves and livestock, officials said, public hunts were crucial to keeping the predators' population in check.